Flat screen color displays normally use illumination in the form of white light. The white light falls on the display such as a liquid crystal display (LCD) which uses color filters to depict colors. Color filters reduce efficiency of the display since large amounts of light are absorbed. Another disadvantage is caused by the color filters that lower the transmittance of the display.
Another method for illuminating displays involves striking dyed nematic crystal panels one after the other. White light is passed through them. Each layer subtracts some amount of the red, blue and green respectively from the white light according to the voltage applied to it and displays the colored image. But this also has a disadvantage of loss of light and hence reduced efficiency. It also suffers from parallax errors.